The present invention pertains to a process for the polymerization of ethylene alone or with comonomers in the presence of conventional free radical generating initiators in a reactor at elevated pressures, wherein lower than conventional polymerization initiation temperatures are employed.
In the past, commercial processes for high pressure polymerization of ethylene have generally been conducted in the presence of oxygen or other high temperature initiators which decompose in the range from about 320.degree. F. to about 640.degree. F. Initiation of polymerization below 320.degree. F. has been economically impractical because of the required large molar quantities of expensive low temperature initiators needed for such purpose. Another disadvantage in using low temperature initiators is that they decompose easily and therefore require special and expensive equipment for the safe storage and handling of these components.
U.S. Pat. No. 4,177,340 discloses that when using oxygen as the polymerization initiator, the start temperature can be lowered to an average value of less than 170.degree. C. (338.degree. F.), e.g., 165.degree. C. (329.degree. F.), by adding to the mixture of ethylene and oxygen from about 0.01 to about 0.5% by weight based on ethylene of certain alkenemonocarboxylic acid esters, e.g., n-butyl acrylate. However, the improvement obtained with this additive is not as great as one would desire, and it is, therefore, an object of this invention to provide a process for the polymerization of ethylene in the presence of relatively high temperature initiators at lower initiation temperatures than heretofore possible with the same initiator system.
Another object is to provide a novel high pressure process for the production of ethylene at increased conversion levels.
A further object is to provide a high pressure polyethylene process wherein capital investment as well as utility costs are reduced.
Further objects will become apparent from a reading of the specification and appended claims.